Building construction sites for large buildings frequently employ aerial lift equipment for tiding operatives to elevated locations for, for example, the installation of overhead pipe work during the construction of a building.
A typical aerial lift may comprise it mobile elevated work platform (MEWP) having an extendable boom which has an elevator basket or cage for housing operatives secured to the end of the boom. The basket may contain a control panel which permits a user standing in the basket or cage to manoeuvre the cage to a raised location which facilitates the carrying out of work. The boom is typically raised by a powered hydraulic system on the vehicle.
The controls in elevator baskets typically include a foot operable safety switch which needs to be closed before control on the operator panel may be operated. If the safety device is released the movement of the basket ceases immediately. However in some situations, operators can become trapped between the MEWP basket and an overhead structure before they can either remove their foot from the foot operable safety switch or operate the emergency stop switch. Operators trapped in this way can be crushed, sometimes fatally.
In EP-A-2096 078, the present applicant has described a safety device comprising a tensioned wire or cord arranged proximate to said controls and an auxiliary safety switch connected in series with the foot safety switch. The foot safety switch is an active switch which the operator must maintain in a closed condition in order to operate the controls. In the event that the cord is distorted the auxiliary safety switch cuts off the foot switch closed signal. This causes the movement of the basket to cease immediately.
The present invention provides an alternative safety device.